1. Technical Field
The present invention relates generally to weld tools for resistance spot welding a joint having two or more sheet metal members and more particularly to a method for sizing weld tools.
2. Discussion
Modern automotive development processes typically employ cross-functional teams having members with diverse backgrounds to review decisions related to the design and manufacture of various components. The diverse backgrounds provides a relatively small team with a broad understanding of almost all of the aspects that are relevant to the design, manufacture and use of the particular component. Accordingly, cross-functional teams have been instrumental in the shortening of the cycle times for developing and producing a vehicle in that the team is frequently able to identify problems and risks in proposed designs and processes prior to physical construction of the vehicle or any related tooling.
While cross-functional teams have made significant advancements, several drawbacks have been identified. One drawback concerns the need for a preliminary design having sufficient detail to properly convey the design concept of the component to team members or tooling suppliers. In the case of sheet metal fabrications, such as vehicle bodies, the design effort undertaken to sufficiently detail a given design for presentation to a cross-function team constitutes a majority of the overall effort required to completely design the sheet metal fabrication to completion. As such, the design of the sheet metal fabrication may be relatively mature prior to the disclosure of the design to the team members, eliminating or substantially impairing the option to introduce significant changes in the design should a notable problem be identified by the cross-functional team.
In particular, problems are routinely encountered with the sizing of weld tools for resistance spot welding the sheet metal members of a joint together. These problems arise when aspects of the design of the joint or the manufacturing process are not fully understood or compensated for in the design process. These aspects include, for example, the ability of the weld tool to equalize to the joint or the need to deflect one or more of the sheet metal members forming the joint into abutment prior to forming the spot weld. The additional force required in such situations often overstresses the weld tool and significantly reduces its useful life.
To avoid reducing the life of a weld tool, it would seem rather obvious to simply procure a larger weld tool for the operation. This alternative, however, is frequently not a viable option due to space constraints that result from the design of the sheet metal fabrication and to a lesser extent, machine tool capabilities. Even where a larger weld tool can be implemented, the machine tool used to orient the weld tool is frequently not sized to handle the additional weight of the larger tool and as such, this change negatively impacts the performance of the machine tool (due to increased inertia and weight) as well as its durability.
Accordingly, there remains a need in the art for a quick, efficient and accurate method for sizing weld tools for resistance spot welding a joint having a plurality of sheet metal members.